We propose to accomplish the following specific goals. (1) To measure the wide band impedance of lamprey spinal giant interneurons using a frequency domain analysis in which the neuron is stimulated with a white noise signal and the impedance (under current clamp conditions) is measured as a function of frequency. (2) To measure the wide band impedance of giant interneurons under conditions in which the cell membrane conductance is changed by membrane polarizaion brought about by current injection, activation of excitatory and inhibitory synapitc input, application of putative transmitters at specific identified dendritic sites and during regeneration following spinal cord injury. (3) To measure the cable parameters of these cells using independent methods. The first will utilize the data obtained from the wide band impedance measurements. These data will be curve fit with a model from which the membrane time constant, dendritic to soma conductance ratio, and dendritic electron length can be estimated. The second will be from morphological measurements of dendritic lengths and diameters from HRP labeled cells. The research outlined in this proposal has as its aim to examine the hypothesis that neuronal integration of synaptic potentials depends on the dynamic membrane properties of the dendritic structure.